On the formation and evolution of asteroid belts and their potential significance for life

TL;DR

This paper explores how asteroid belts form near the snow line in protoplanetary discs, their potential role in life's evolution, and how observations of exoplanet systems relate to their prevalence.

Contribution

It combines numerical models and observational data to analyze the formation, location, and potential significance of asteroid belts in exoplanetary systems.

Findings

Asteroid belts likely form near the snow line in protoplanetary discs.

Most observed giant planets are inside the snow line, suggesting fewer belts outside.

The scarcity of giant planets outside the snow line may imply that asteroid belts and complex life are uncommon.

Abstract

Suggestions have been made that asteroid belts may be important both for the existence of life and perhaps even for the evolution of complex life on a planet. Using numerical models for protoplanetary discs we calculate the location of the snow line, and we propose that asteroid belts are most likely to form in its vicinity. We then show that observations of warm dust in exo-solar systems, thought to be produced by collisions between asteroids in a belt, indicate that asteroid belts (when they exist), indeed coincide with the radial location and the temperature of the snow line. Giant planets form outside the snow line and prevent planet formation just inside of their orbit creating an asteroid belt there. However, the migration of giant planets through the asteroid belt likely disperses the compact formation. We examine existing observations of giant exo-planets and find that less than 4% are at radial locations outside of the snow line. This definitely may be the consequence of observational selection effects. However, with this caveat in mind, we point out that the dearth of giant planets outside the snow line may also suggest that compact asteroid belts are not common, and more speculatively that complex life may not expected in most of the currently observed systems.